US2407870A - Variable load brake apparatus - Google Patents

Description

Sept. 17, 1946. E. s. COOK VARIABLE LOAD BRAKE APPARATUS Filed Dec. 28, 1944 Patented Sept. 17, 194-6 1 VARIABLE LOAD BRAKE APPARATUS Earle S. Cook, Forest Hills, Pa., assignor to The Westinghouse Air Brake Company, Wilmerding, Pa., a corporation of Pennsylvania Application December 28, 1944, Serial No. 570,053

This invention relates to variable load brake equipment for vehicles, and more particularly to that type of equipment which is constructed and arranged to be automatically adjusted or conditioned to vary the braking force according to the position that the vehicle body, under various loads, assumes relative to a fixed part of a truck.

The present trend toward the use of light weight materials in the construction of railway freight cars has resulted in much higher ratios of gross weight to tare weight than ever before encountered. Since the braking force with relation to the weight of an empty car must be such as to avoid wheel sliding and excessive train shock, the braking force on lighter weight cars will consequently have'to be lower than heretofore. Because the gross weight of the car is limited only by the load limit for the trucks, which remains unchanged, the lower braking force will be inadequate for proper control of such cars when loaded.

The principal object of this invention, therefore, is to provide a variable load brake equipment which will operate in conjunction with the present type of fluid pressure freight brake equipment so that the braking force will be sufliciently low on an empty car to prevent wheel sliding and will be increased in relation to any increase in the gross weight of the car so'that a loaded or partially loaded car may be properly controlled in a train.

Another object is to provide a variable load brake equipment which will require a single standard auxiliary reservoir and a single brake cylinder device and which will operate in conjunction with the standard fluid pressure freight brake equipment to obtain the present application and release time intervals on a car without altering the flow capacities of any passages in the presentstandard freight brake equipment.

Another object is to provide a variable load brake equipment which will prevent the produc tion of undesirably high braking forces on an empty or a lightly loaded vehicle by an over- 2s Claims. (01. 303-22) plication of the standard freight brake equipment available for use by the train operator.

Another object is to provide a variable load brake equipment of the type employing a single brake cylinder device in which the fluid pressure may be varied according to the degree of brake application, the pressure for any given application being proportioned according to the weight of the load carried by the vehicle.

To attain these objects the variable load brake mechanism embodying this invention employs a single brake cylinder device, which is preferably of larger diameter than the standard device, for providing the braking force for a fully loaded vehicle. The lower degree of braking force which is necessary for vehicles carrying lighter loads is obtained by the use of a relay valve mechanism ofthe scale beam type which is arranged to operate in response to the pressure of fluid in the brake cylinder device to spill or bleed fluid under pressure from the brake cylinder device orbrake cylinderpipe into a volume reservoir until the degree of pressure of fluid in said reservoir is svufl'icient to balancewith the brake cylinder pressure, thereby reducing the pressure of fluid inthe brake cylinder device according to thefweight of the lading carried by the vehicle as determined by the position of the fulcrum along the scale beam. The fulcrum is positioned, according to the weight of the load carried, by a mechanism which is responsiveto fluid under pressure supplied from the brake pipe when the brake pipe is below a certain degree of pressure to initially actuate a measuring element into engagement with the top of a vehicle axle and thereafter to displace the fulcrum distances progressively increasing as the weight of the lading increases. i

A feature of this variable load brake mechanism is the use of an intercepting valve device interposed in the communication between the brake controlling valve device and the auxiliary reservoir and operative to close off said communication during a brake application if the pressure of fluid in the auxiliary reservoir is reduced more than a fixed amount, such as twenty pounds, below that at the initiation of the brake application. Upon releaseof the brakes the intercepting valve device will reset to measure the fixed amount of twenty pounds reduction in fluid pres sure from the pressure to which the auxiliary reservoir has been recharged, and upon a further reduction of twenty pounds will again close off the communication.

Other objects and advantages will appear in the following more detailed description of the invention.

In the accompanying drawing the single figure is a diagrammatic view mainly in section of a variable load brake equipment embodying the invention.

As shown in the drawing, the variable load fluid pressure brake equipment may comprise the usual brake pipe I', a branch pipe 2, a-brake controlling valve device 3, a cut-01f valve device 4, a load measuring apparatus 5, a check valve device 6, a locking mechanism 1, a variable load valve mechanism 8, a service volume reservoir 9, an emergency volume reservoir 18, an intercepting valve device I l, a brake cylinder device I2, an auxiliary reservoir 13, an emergency res-- ervoir l4, and a retaining valve device I5. I

The brake controlling valve device 3 shown is of the AB type but may be of an other de sired type. thewsame construction and have the same. operating characteristics as the AB valve device fully described inthe patent to .Clyde C. Farmer, No; 2,031,213, issued, February. 18,. 193.6, and ,assigned to theassignee of the, present invention, aridzin view of this it is deemed unnecessary to show and describe this devicein detail. It will, of course, be understood that this device operates upon a service. reduction in brake pipe pressure to supply fluid under pressure to effect a service. applicationof the brakes, upon an emergency reduction in brake pipe pressure to efiect an emergency applicationof th brakes,v and .upon an increase inbrake pipe pressure to efiect a release of the brakes and the ohargingof the brake equipment.

The cut-01f valve device 4 may. comprise a'casing in .which there ismounted. a flexible .diaphragm 6, at one side of which is a chamber .11 in constant .open communication with the atmosphere. by way of a passage-1.8. sideof the diaphragm is a valvechamber .i 9. which is in constant open communication (b Way of a connected pipe and passage :za withabrake pipe passage 2 I provided in the brake controlling valve device .3. Slidablymounted inchamber ll is a stop member 22 which is arranged to abut either a shoulder 23 formed on the wall of .the chain-.- ber1 to limit the upward movement of theimemher, or a ring. 24, expanded into an annular groovein said wall, tollimit the. downward movement of said..member.. Interposed between and operatively engaging the member 22 and the top wall. of the chamber i1 is a spring '25 which, at all times, tends to move the stop member downwardly. Contained in the chamber [.9 is a slide valve 126 which is arranged to be operated by .a notched stem or follower 21 operatively secured to the flexible diaphragm I6 for controlling the operation of the locking mechanism 1 and the load measuring apparatus, and for also controlling a communication to the emergency volume reservoir It, as will hereinafter more fully appea-.

The cut-off valve device 4 is provided with a loading mechanism for the purpose of preventin-g; fluid under pressure, acting on the under side of the slide valve 26, from raising the valve from itsseat when the pressure of fluid in the-valve chamber I9 is reduced. This mechanism may comprise a flexible diaphragm 28 which is mounted in the cut-off valve device casing and which operatively engages a rocking pin 29 through which a loading force is adapted to be transmitted to the slide valve 26. 'Thefvalve chamber This device may be of substantially At..the other I9 is open to the under side of the diaphragm and at the other side of the diaphragm there is a chamber 31] which is in constant open communication with the atmosphere by way of a passage 3!. Contained in the chamber 39 and interposed between and engaging the, valve casing andv the diaphragm 28 is a spring 32 which produces the loading force to hold the slid valve 2 6" on its seat.

The load measuring apparatus '5 may be'of any desired construction but for illustrative purposes is shown as comprising a bracket 33 which isrigidly secured by any suitable means to any convenient part of the vehicle body such for instance as to the lower cover plate of a center sill 34 of which only the bottom cover plate is shown The bracket includes the arms 35 and 36 on which are operatively mounted a linkage or measuring mechanism 3! comprising a measuring element 38 having a horizontal portion 33, disposed above the central portion of an axle 40 and parallel to the bottom of the center sill 34, and having a downwardly depending pore tion 4! which is normally spaced away from the axle a sufficient distance so that it will not be engaged by the axle 40 when the vehicl is subject to the usual service shocks, Extendin between the arms 35 and 36' and the measuringelement 38 and operatively connected thereto are vertically spaced links 42 and 43, link 42 having one end pivotally connected by means of a pin 44 to the arm35 and having the other end connected by means of a pin 45 to the upper end of the portion 4| of the measuring element, 33. One end of the link 43 is pivotally connected by means of a pin 46 to the arm 36 and the other end is connected by means of a pin 41 to the lower end of the depending portion 4! of the measuring .element. The axes of the pivot points at each end of thelinks 42 and 43 are in vertie cal alignment and spaced apart equal distances vertically was to maintain the portion ,39-substantially parallel with the center sill 34' in all positions of the linkage. The links 42 and .43 are each provided with a series of corresponding holes 48 and 49, respectively, for receiving the pins 45 and 41, respectively, to obtain a di-fi'er ent degree of total vertical travel of the measur-' ingelement 38 to meet varied conditions, asset forth in the copending patent application of Claude A. Nelson et al., Serial No. 551,200, filed August 25, 1944, now Patent No. 2,402,434, issued June 18, 1946, and assignedto the assignee ofthe present application, in which the load measuring mechanism 5 is fully disclosed and claimed. 0perati-vely connected between a lug 53' on the element 38 and a lug 5!- on the centersill 34 is a tension spring 52 which, at all times, tends to move the measuring element toward the position in which it is shown and to normally hold the element in this position-against accidental movement therefrom. For limiting the upward travel of the'elemen-t 38, the horizontal portionis pro vided'with a stopmember 53 which engages the bottom of center sill 34- and is adjustable'in the portion 39 by screw-thread means. Archer-54 is mounted by means of" a pin 55 on one end of a supporting member 56, which member is pivotally mounted. at its other end to the arm 36 by means of the pin 46. For imparting movement to the element .38, the roller is coupled to the lower end of the portion 4| by means of a strut member '51 which is mounted at its one end on the pin 55 and at its other end on the t r in 4 ..T e irui embe isp qv deda the .latterend with a series of holes 58 foradjusting the coupling betweenthe roller 54 andthe element 38 when a change is made. in the location of the pin 47 in the link 43.

For actuating the roller 54, the load measuringapparatus 5 is a fluidpressure controlled mechanism comprising a casing which is integral with the bracket 33 and which is provided with apiston 59 having at one side a chamber 69 which is in constant open communication with the atmosphere by way of. a passage 6|, which chamber contains a spring 62 engaging a wall 63 of the chamber 69 and the non-pressurefside of the piston 59 so as to tend to move the piston toward the position in which it is shown; A stem 64 of the piston 59 extends through chamber 69 and an opening in the wall 63 and is pivotally connected, by means of a pin 65 with a shiftable lever,66'at a point intermediate the ends of the lever. For purposes which will more fully appear later, this lever 66 is located so that its lower end may be actuated into operative engagement with roller 54.

At the other side of the piston 59 is a chamber BIwhich is in constant open communication, by way of pipe and passages 68, with a valve chamber 69 of the check valve device 6. This chamber 69 contains a ball check valve I9, the under side of which is connected to a locking mechanism I by way of pipe and passages I I. The check valve device 6 is ,further provided with a passage .12 which by-passes the ball check valve and is of small flow capacity to insure the occurrence of the locking operation of the mechanism 1. before the chamber 61 is depleted of fluid under pressure, as will hereinafter more fully appear.

The locking mechanism 1 comprises a casing which is provided with a piston I3 having atone side a chamber I4- which is in constant open communication with the cut-off valve device 4 by way of a connected pipe and passage I5. At the other side of the piston is a chamber 16 which is in constant open communicationwith the atmosphere by way of a passage 11. This chamber I6. contains a spring I8 which operatively engages the bottom surface of the chamber and the piston I3 so asto tend to move the piston toward the position in which it is shown. A stem "I9 attached to the piston I3 extends downwardly through the chamber 16 and terminates in a locking portion 89 which is slidably mountedin a guide opening BI formed in the bottom portion of the casing of the mechanism. The locking portion 89 of the piston stem has a transverse opening 82 which is arranged to register with openings 83 formed in the wall of the opening 8!. The upper surface of the bottom wall of the opening 82 in the locking portion 99 is toothed for locking engagement with a correspondingly toothed portion 84 formed on one end of a fulcrum positioning bar 85, the opening 82 being large enough to provide sufiicient clearance for moving the look-- ing portion 89 of the stem I9 downwardly out of engagement with the bar.

Intermediate its ends, the bar 85 is operably connected to the lever 66 by means of a pin 86 which extends through a slot 81 formed in the upper end of the lever 66, the slot providing for the necessary relative movement between the lever and the bar whenthey are operated. Rotatably connected to the right-hand end of the bar 85 by means of a pin 88 is a fulcrum member 89 which may be shifted in the variable load valve mechanism 8 in a manner to be more fully describedlater. Encircling the. bar 851s a helical spring 99 which engages a casing .9I of the mechanism 8 at one end and the lever 96 at the other end so as to urge the leveryand thereby the bar 85, and fulcrum member 89 of the mechanism 8 toward the position in which they are shown.

The variable load valve mechanism 8 may comprise the casing 9I having a recess formed therein and having secured to the bottom. thereof in any suitable manner a cap portion 92 which closes the open end of said recess, the inner surfaces of the recess and the cap portion defininga chamber 93 which is constantly open at the lefthand end to the atmosphere. 7 This chamber contains the fulcrum member 89 and a scale beam lever 94 arranged to rock on the fulcrum member. Secured in any suitable manner to the top of the casing 9I is a cap portion 95, there being a sealing gasket 96 clamped between the casing SI and the cap portion. This gasket96 comprises laterally spaced flexible diaphragms 97 and 98 which ar preferablyof substantially the same area.

At one side of thediaphragm 91 there is a chamber 99 Which is open at all times to the at: mosphere by way of an opening I99 and the atmospheric chamber 93 in the casing 9|. Contained in this chamber 99 and operatively engaged by the diaphragm 91 is a follower I9I having a stem I92 which extends throughjan opening in the casing, and which, at its lower end, is pivotally connected with the scale beam lever 94 at a point located a short distance from its lefthand end. At the other side of the diaphragm 91 is a chamber I93 which is open to the under side of a valve I94 by way of a fluted stem I95 of the .valve, which stem extends into chamber I93 and is arranged to be engaged by the diaphragm 91 so that the valve may be operated to control the flow of fluid under pressure to said chamber, whence it may flow to the service volume reservoir 9 by way of a passage I95, a pipe I91, and a pipe I98. The passage I96 is also open to the under side of a ball check valve I99 and the pipe I9? is also open to the slide valve seat of the cut-off valve device 4.

The valve I94 is contained in a chamber II9 formed in the cap portion 95, which chamber is closed at the top by a cap nut III. This chamber is in open communication with a chamber I I 2 containing the ball check valve I99 by way of a passage H3 and also is in open communication with the brake cylinder device I2 by way of a passage H4 and pipe II5. Interposed between the cap nut III and the valve I94 is a spring IIB which at all times urges said valve toward its seating position.

At one side of the diaphragm 98 is a chamber III which is open at all times to atmosphere by way of an opening H8 in the casing 9| and the atmospheric chamber 93. Contained in this chamber I I1 and operatively engaged by the diaphragm 98 is a follower II9 having a stem I29 which extends through an opening in the casing and which, at its lower end, is pivotally connected with the right-hand end of the lever 94. At the other side of the diaphragm 98 is a chamber IZI which is in constant open communication with the passag I I4,

The intercepting valve device II comprises a casing and diaphragm I22 rigidly clamped around its periphery between two connected parts of the casing, and having, at one side, a chamber I 29 which, as shown, may be connected with the auxiliary reservoir I3 by way of a valve chamber I24, p ssa e '25 an p e. .A he th s d 0.4-

the diaphragm I 22 is a springchamber I21 which 7 is'inconstantopen communication with the brake controlling valve device 3 by way of a connected pipe and a-passage I28 and is in valvecontrolled communication with the auxiliary reservoir I3 by wayof passages I29 in a wall I30 of the casing, a'valve chamber I3I, passage I25 and pipe I 25.

Contained in the valve chamber I24 is a valve I32 having a fluted stem l 33 which extends through a'suitable bore in the casing se that its lower end may be operatively engaged by a portionof a follower I34 secured to the diaphragm I22. Interposed between and operatively engaging'a cap nut I35 at the topof the chamber I24 and the valve I32 is a spring I33 which urges said valve toward its seated position. 7

Contained in the chamber I3I is a valve I31 arranged to engag a valve seat I38 formed in the bottom wall of the chamber and thereby interrupt the communication between the auxiliary reservoir I3 and the brake controlling valve device 3 as will later more fully appear. For limiting theupward movement of the valve I31, said valve is provided with a flange I39 which normally engages the bottom surface of the wall I30 between chambers I21 and I3I. The valve I31. is secured byscrew-thread or other suitable means to a gui'd member I 40 which is slidably mounted in a suitable sleeve portion M! of the wall I39 which sleeve portion is contained in chamber I21.

Contained in chamber I21 and interposed between the upper flanged 'end of the guide member I 4 and the wall I39 is a coil spring 442- which encircles the sleeve portion I M and the guide member I40 and constantly urges the guide memher, and thereby the valve I31, toward their upper positions, in which position the flange I39 of the valve I3?! abuts the wall I3B.- As explained later, this spring I42 is a reduction limiting spring which determines when th valve I31 will be moved into its lower seated position. Contained in a recess 143 formed in the guide member I40 is a spring I44, the upper end of which operatively engages the under side of the diaphragm follower I34 and the lower end engages the bottom wall 'of' the recess. This spring exerts an upwardly directed force on the follower I34 so as to cause the follower to normally engage the bottom of stem I33 of the valve l32 and hold the valve in its unseated position. as shown.

OPERATION Initial charging of the equipment Assuming the vehicle embodying the invention to be empty or separated from a train, the brakes on the vehicle released, the brake pipe 'I on the vehicle depleted of fluid under pressure and the fulcrum member 89 of the variable load valve mechanism 8 temporarily disposed in the empty position in which it is shown, the brake controlling valve device 3 will be in brake applied position and the several other parts of the equipment will be in the positions in which they are shown.

Now if the empty vehicle is placed in a train, the brake pipe I will of course be connected at each end of the vehicle to the corresponding brake pipe at the adjacent end of each-adjacent vehicle of the train and as a result" the brake equipment will be in condition'to be charged with fluid under pressure in the usual manner. In initially charging the equipment fluid under pressure supplied in the usual manner to the brake pipe I flows througha branch pipe -2 to the chambers at'the facesof the service and emergency pistons of the brake controlling valve device 3, moving the pistons indue courseto ,release'a-nd charging position. Fluid under pressurewillthen flow to the several chambers of the brake con-, trolling valve device 3, and thence in the usual manner, to the auxiliary reservoir 13 bywayof the pipe I123, the chamber I21, passages I29, chamber I'3I, and passage I25 in the intercepting valve device I I, and pipe I26, and to the emergency reservoir I4 by way of a pipe I45 Atthe same time, fluid under pressur will also .flow from the :brake pipe I through passage 21 and connected pipe and passage 20 to valve-chamber I9 in the cut-off valve device 4. From 'chamber I9. fluid under pressure flows through pipe and passage 15 to chamber 14 of the .lockingmechanism 1. Upon an increase in the pressure of. fluid in this chamber 14 to a predetermined. value, the piston 13 is caused tomove downwardly against the opposing pressure of the spring 18, thereby moving; the toothed locking portion out of locking engagement with the toothed portion 84 of the bar 85, thus releasing the bar.

The piston 13 as it moves downwardly passes the mouth of the passage 1I, thereby establishing communication between chamber 14 of: the locking mechanism and chamber 31 of the load measuring apparatus by way of said passage and check valve device 6. Fluid under pressure will flow from chamber 14 through. pipeand. passage H, and passage 12 to passage and pipe 68 and also past ball check valve 13 to chamber69 in the check valve device 6, and thence byway of pipe and passage '68 .to chamber Bland therefore to the face of the piston. 59. In response to the pressure of fluid thus supplied to chamber 61, piston 59 will move to the right against the opposing pressure of spring 62, effecting through the: medium of the stem 64 and pin. 65, the movement of the lever 66. Since the upper endof the lever 66 isheld in its left-hand position by the pressure of the spring 93 the lever will be caused to rock in a'counterclockwise directionaboutthe pin..86.' As the .lever' rocks in this manner it angages the roller 54 of the measuring mechanism 36; causing the connected members 56, roller. 54 and pin 55 to rock in a clockwise direction. about the pin 46. The member 51, being coupled cdi rectly to the \pinz55 and to the pin 41 andthereby to member .56 and portion M of the measuring element; will force the element 38 downwardly against the opposing force of spring 52 until the bottom surface of the portion 39 of the element engages the'periphery of the axle 40 at a point located substantially at the middleo'f its length,

the links 42 and '43 rotating in unison inaclocke wise direction to so control the element 'as to maintain the bottom surface of the arm 39 thereof in. substantiall parallel relation to the horizontal plane of the adjacent surface of the central portioniof the axle 40. I With the vehicle empty, the movement of the piston 59' will be taken up entirely in actuating the load measuring mechanism 36 and therefore nomovement will be imparted to the fulcrum deflect upwardly against the opposing pressure of the spring 25. The diaphragm, as it is thus deflected, acts .through the medium of the stem or follower 21 to shift the slide valve 26 to its uppermost position, in which position a cavity I46 in the valve connects pipe and passage 15 and a pipe and passage I41 to a passage I48 which leads to the atmosphere. With this connection thus established, fluid under pressure in piston chamber 14 of the locking mechanism 1 will be vented to atmosphere by way of pipe and passage 15, cavity I46 and passage I48. Also, fluid under pressure will flow from chamber 61 of the load measuring apparatus 5 through pipe and passage 68, passage 12 of the check valve device 6, pipe and passage H to chamber 14. Since passage 12 is of restricted flow capacity, the fluid pressure in chamber 14 will reduce much more rapidly than in chamber 61.

When the pressure of fluid in chamber 14 is slightly less than that of the spring 18, said spring will act to shift the piston 13 upwardly, bringing the locking portion 80, through the medium of the stem 19 into locking engagement with the toothed portion 84 of the fulcrum shifting bar 85. With the piston 13 in its uppermost position, pipe and passage II are connected to atmosphere by way of chamber 16 and a passage 11 in the casing and leading from chamber 16 to the atmosphere. Fluid under pressure flows from chamber 61 through pipe 68, passage 12 and pipe 1| .to chamber 16 and thence to atmosphere by way of passage 11. Whenthe fluid pressure in chamber 61 acting upon piston 59 is slightly less than the opposing pressure of the spring 02, said spring will cause the piston 61, stem 64 and the lever 66 to return to the positions in which they are shown. With the force of piston 59 which operates the measuring mechanism 31 removed, the spring 52' will act to retract the measuring mechanism to the position in which it is shown.

From the preceding paragraph it will be ob served that the locking mechanism I is always operated to lock the fulcrum shifting bar 05, and thereby fulcrum member 89 of the variable load valve mechanism 0, beforethe measuring mechanism 31 is retracted from contact with the axle. With the chambers 61 and 14 thus vented of fluid under pressure, lock controlling piston 13, measuring apparatus controlling piston 59, and lever 0 66 which had been previously displaced are now returned to the position to which they are shown, and, with the cut-off valve device 4 being maintained by fluid at brake pipe pressure in the position to which it was previously moved, the equipment is now conditioned for braking an empty vehicle.

Service application of the brakes on an empty vehicle When it is desired to effect an application of V the brakes, the brake pipe pressure is reduced in the usual manner, causing the brake controlling valve device 3 to function to supply fluid under pressure from the auxiliary reservoir I3 to the brake cylinder device I2 by way of the intercepting valve device I I in order to advance the usual brake shoes, notshown, into frictional engagement with th vehicle wheels. The flow of fluid under pressure from the auxiliary reservoir I3 to the brake cylinder device I2 is by way of a pipe I26, passage I25 in the intercepting valve device II, past valve seat I33 and valve I31 into chamber I3I thence through passages I29 to chamber I21 andpipe I28, through the brake control valve device 3 and brake cylinder pipe I49. At the same time, fluid under pressure flows from the brake cylinder pipe I49 through pipe II5 andpassage II4 to chamber I 2| in the variable load valve mechanism 8, and by way of passage I I4 to valve chamber H0, and thence by way of passage II3 to checkvalve chamber H2. Fluid under pressure thus supplied to chamber I2I causes the diaphragm 98 to flex downwardly, and the diaphragm 98 as it is thus being flexed acts through the medium of the follower H9 and follower stem I20 to rock the lever 94 about the fulcrum member 89 in a clockwise direction, the lever 94 as is thus operated acting through the medium of the follower stem I02, follower ml, and diaphragm 91 to cause the valve I04 to be unseated against the opposing pressure of the spring IIS and of the fluid in chamber II 0 acting on the valve. With the valve I04 unseated, flUlid under pressure flows from the valve chamber IIO past the unseated valve I04 and its fluted stem I05 into chamber I03, from whence it flows by way of passag I06, pipes J01 and I08 to the service vol.- ume reservoir 9.

It should here be noted that at this time the slide valve 26 of the cut-off valve device 4 will be in its uppermost position, in which position com munication between pipe I01 and emergency volume reservoir I0 is closed, and there will therefore be no flow of fluid under pressure from the brake cylinder pipe to the emergency volume reservoir I0.

When the pressure of fluid in diaphragm chamber I93 of the variable load valve mechanism 8 and consequently in the reservoir 9 becomes suflle cient to overcome the pressure of fluid in chamber I2I acting in the opposit direction on the lever 94, the diaphragm 91 will be caused to flex in a downward direction and thereby permit ,the spring I Hi to seat the valve I04, closing off the further flow of fluid under pressure to volume reservoir 9. Sinc further build-up of pressure in chamber I03 can not occur, the lever 94will come to rest in the position in which it is shown.

It will here be understood that the brake leverage ratio and the brake cylinder volume will be such as to be able to attain with a single brake cylinder the maximum braking required, or in other words to attain the desired degree of braking for a fully loaded vehicle. From the foregoing paragraph it is apparent that, when a service application of the brakes is effected with the fulcrum member 89 in the position in which it is shown, the maximum amount of fluid under pressure is spilled or bled from the brake cylinder pipe I49 intothe service volume reservoir 9 and consequently there is obtained the minimum brake cylinder pressure for a given reduction in brake pipe pressure. As will hereinafter more fully appear the fulcrum member 89 is shifted to the right from the position in which it is shown in accordance with the added weight of any lading placed on the vehicle, so that the leverage or mechanical advantage will be resolved in favor of the diaphragm 91. Consequently the pressure of fluid in chamber I03 will not have to become as high as that in chamber I2I in order to seat the valve I04 and terminate the flow of fluid under pressure from the brake cylinder pipe I49 to th volume reservoir. Thus, as the weight of the load carried by the vehicle is increased, the amount of fluid under pressure that will. flow to the volume reservoir is decreased and as a consequence the force exerted by the brake cylinder device, forany degree of brake pipe reduction, will'increase as the load increases. T

past valve I31, through the chamber I3I, passage I23, chamber I21 and passage andpipe I28 to the brake controlling valve device 3. Because the volume of chamber E23 is larger than the combined volume of. chamber I2! and I3I and by, reason of a choke I250, in passage I25 as shown, the.pressure of fluid in chamber I27 will reducemore rapidly than that in chamber I23. Inresponse to the excess of fluid pressure acting on the upper side of the diaphragm I22 the diaphragm will be caused to deflect. downwardly againstthe opposing pressure of the spring I44 until the bottcmlof the follower I34 engages the top. of the guide member I43, the downward movement Of said guide member being stopped at this time by the action of the spring I42. However, this-movement of the follower I34 will be suflicient to-permitthespring I36 to actuate the valve.l'32ito its seated position. The pressure of. fluid thus bottled up .in chamber I23 is now the. standard with. which the. pressure of fluid at reducedauxiliary reservoir pressure in chamber I21 will be compared.

If the brake controlling valve device 3 continuesto operate tosupply fluid under pressure from the. auxiliary. reservoir I3 to the brake cylinder. device 12 in theapplioation of the brakes just previousl described, the pressure of fluid in.the auxiliary reservoir I3, and consequently in the interconnected chamber I21, will continue to decrease .untilthe pressuretherein is 20 pounds less than that. in chamber I23, at which time the diaphragm I22 willbecaused by the higher pressure inchamber against the opposing pressure of spring I42. The diaphragm, as it is thus deflected; acts through the medium of the follower I 34 and guide -mem-. ber I43 to move the valve I3! downwardly to its lowermost position; in which position'said valve engages the valve seat I38 With-the valve- I3! thusseated, the flowof fluid under pressure 'from the auxiliary reservoir I3 tothe valve device 3 occurring during a. service application of the brakes will be terminated for that brake application, regardless of the degree-of brake pipe reduction.

Release of a service application of the brakes on an empty vehicle Whenit. is desired. to effect the release of the brakes, the brake. pipe pressure is increased in the usual manner, causing the brake controlling valve device 3- to' functionto establish communicationfrom a brake cylinder device I2'to atmos-' phere by'way'of the retaining valve device I5. Fluid under pressurenow'flowsby way of pipe I 43 from the brake cylinder'device I2 to the brake controlling valve device 3 and from there byway of pipe lfiiltothe retaining-valve device I which connects pipe I53 directly tothe: atmosphere when a'handle I51 on device -I 5 is in the position inwhich it is shown. The brake cylinder device I2 nowrespondsto-the releaseof fluid under pressure therefrom in the usual manner to effect arel'ease-ofthevehiclebrakes.

Valve chamber 1 i il-and chamber "I 2 I 'being connected by way ofpassageII4'and pipe' II5'to I23 to deflect downwardly brake cylinder pipe I43, fluid under pressure-will flow from these chambers to the atmospherewith the'fluid under pressure flowing from the brake cylinder device I2. Valve chamber I I2 being-connected to Valve chamber III] by way of passage I I3, fluid under pressure therein will also flow to atmosphere by the same route. With the pressure of fluid in chamber II2 reduced'dueto-the flow of fluid therefrom, the pressure of fluid-beneath the ball check valve I03 will lift the check valve to permit the flow of fluidfrom the ser-vice volume reservoir 3 to atmosphere by wayof pipes I38 and I31, andpassage I 33 past the'unseated check valve I33 into chamber H2 which-isnovv connected to atmosphere byway of therout'e previously described. Fluid under pressure in chamber I03 may also flow by way'of passaJgelilS and past ball check valve I09 intovalve chamber I I2 and thence to atmosphere.

Th brake controlling valve device? also functions at this time to supply fluid under pressure from the brake pipe- I to the auxiliary and emergency reservoirs I3and I4, respectively. As previously described in connection with initial charging of the equipment, fluid under pressure in brake pipe I will flow through branch pipe 2 to the brake controlling valve'device 3 and from thence by way of connected pipe and passage'IZIl to chamber I2! in the intercepting valve device II, through passages I29'to chamber I 3|. When the pressure of fluid in chamber I21 locatedat the underside of the diaphragm I22 is withinless than twenty pounds of that inchamber I23; the spring I42 will act to move the guide member I43 and thereby the valve I31, upwardly'until the flange I39 of said valve engages-the bottom surface of the wall I33 formed in the casing. With the valve I31 thus positioned out of engagement with the seat I38, as shown in the drawing, communication is established by whichfluid under pressure supplied from the brake pipe I to chamber I21 flows past valve seat I33, through passage I25 and pipe I26 to auxiliary reservoir I3.

The guide member I 40 as'it is being moved up wardly, effects,"through the medium of a follower I34, an upward deflection of the diaphragm I22.

Upon a further build-up of pressure in chamber I21 spring I 44 will be permitted to move'the dia phragm I22 upward, thereby moving the follower I34 out of engagement with the member I43. Thereafter a further increase'in thefluidpressure in chamber I21 will cause diaphragm I22't0 deflect upwardly and act through the medium'of the follower I34 and valve stem I33 to move the valve" I32 upwardly, against the opposing pressure of a spring I36, to its unseated position. With the valve I32 unseated, fluid under pressure supplied to passage I25 for chargingthe auxiliar reservoir I3 will also flow through chamber I24, past valve I32 and fluted valve stem I33 into chamber I23, charging chamber I23 with fluidat auxiliary reservoir pressure.

In connection withthe foregoing description it should be mentioned that, with the" brake controlling valve device of the standardfluid pressure. brake equipment now in use operating in the usual manner in response to a full service brake application, when the brake pipe pressure has. been reduced'from' seventy pounds to approximately fifty pounds; the'auxiliary reservoir will be in" open communication with the brake cylinder andas a consequence the auxiliar reservoir: pressure will equalize with'the brake cylinder pressure at approximately fifty pounds whichcorresponds with the reduced'brake pipe move to their emergency positions.

13 pressure. Since the pressures of fluid in the auxiliary reservoir and brake cylinder arenow equal, a further reduction in brake pipe pressure cannot increase the pressure of fluid in the brake cylinder.

It will be apparent to those familiar with the operation of the standard fluid pressure brake equipment mentioned in the preceding paragraph that if the intercepting valve II were omitted and the remaining features of the invention were combined with the brake controlling valve device 3, certain undesirable operations may occur. For example, when a full service reduction of twenty pounds in brake pipe pressure is effected, the brake controlling valve device will of course move to application position and in this position will supply fluid under pressure from the auxiliary reservoir to the brake cylinder, and to the servicevolume reservoir 9 also if the vehicle is empty or lightly loaded. The amount of fluid flowing from the auxiliary reservoir will b substantially the same as in the standard brake equipment. Since the volume of the brake cylinder, to which may be added the volume of the service volume reservoir, is greater than that of the standard brake cylinder, the pressure of the brake cylinder will be substantially less for a full service reduction in brake pipe pressure. When, due to the flow of fluid from the auxiliary reservoir to the brake cylinder andvolume reservoir 9, the auxiliary reservoir pressure reduces slightly below the reduced brake pipe pressure (fifty pounds), the brake controllin valve device will move to lap position and thereby out oi? the flow of fluid from the auxiliary reservoir. In this position the brake controlling valve device will bottle up the fluid in the auxiliary reservoir at a higher pressure than has been attained in the brake cylinder, so that if a further reduction were effected the brake controlling valve device would function to again supply fluid under pressure from the auxiliary reservoir to the brake cylinder and service volume reservoir and thus effect an increase in the pressure of fluid in the brake cylinder beyond a safe or desirable degree. As will hereinafter more fully appear, such an undesirable condition is most likely to occur in cycling the brakes in descending a grade, that is to say, in alternately effecting an application of the brakes and then recharging the equipment partially while a partial release is taking place through the usual retaining valve device which has previously been set to retain a predetermined pressure in the brake cylinder. It will be apparent from the foregoing description that by the use of the intercepting valve device II this undesirable increasing of brake cylinder pressure due to an over-reduction in brake pipe pressure, which may be effected in cycling the brakes, is entirely eliminated since the device functions in response to a twenty pound reduction in auxiliary reservoir pressure from any pressure to which the reservoir is recharged to close the supply communication from the auxiliary reservoir to the brake controlling valve device.

Emergency application of the brakes on an empty,

vehicle When it is desired to effect an emergency application of the brakes, an emergency reduction in brake pipe pressure is effected in the usual Well known manner which causes the several parts of the brake controlling valve device 3 to With the operating parts in their emergency positions, communication is established by which fluid under pressure is supplied from both the auxiliary reservoir I3 and the emergency reservoir I4 through pipe I49 to the brake cylinder device I2 to obtain greater brake cylinder pressure than that obtained by a full service application.

A previously described for a service application of the brakes on an empty vehicle, fluid under pressure in pipe I49 also flows by way of pipe I I5 and passage II4 to chambers I2I and III) in the variable load valve mechanism 8. In response to the pressure of fluid in chamber I2I acting upon diaphragm 98, said diaphragm deflects downwardly and acts through'the medium of follower I I9 and stem I253 to rock the lever 94 about the fulcrum member 89 in a clockwise direction, the lever, as it is thus being rocked, acting through the medium of the stem I02, follower IIlI, diaphragm iii, and valve stem I05 against the opposing pressure of spring II 6 to unseat the valve I04. Fluid under pressure supplied from the auxiliary and emergency reservoirs I3 and I l, respectively, to chamber IIO now flows past valve I94 and fluted valve stem I05 into chamber I03, whence it will flow to the service volume reservoir 9 by way of passage I06, pipe I01 and pipe I08.

In the description of the effecting of a service application of the brakes on an empty vehicle, it was noted that the flow of fluid from the brake cylinder device I 2 was terminated when the fluid pressure in the service volume reservoir 9, and therefore in chamber I54 acting upon diaphragm 91, was high enough to counterbalance the brake cylinder pressure in chamber I2I actingupon diaphragm 98 so as to permit valve I64 to seat. Obviously, if the cubic content of the brake cylinder device I2 were greater, the brake cylinder pressure at the time when valve IE3 is seated would be higher, or if the cubic content of the reservoir 9 were greater, the brake cylinder pressure would be lower at the time When the valve I M was seated. Since during an emergency application the brake cylinder pressure is increased and also the auxiliary and emergency reservoirs are both open to the brake cylinder device, thereby adding their volumes to the brake cylinder volume, means are provided for connecting the emergency volume reservoir I ii to reservoir 9 as a supplementary volume in order to prevent the occurrence of an unreasonably high or unsafe brake cylinder pressure.

When an emergency reduction in brake pipe pressure is effected, the brake pipe I is depleted of fluid under pressure in the usual manner by the brake controlling valve device 3. Since chamber I9 in the cut ofi valve device 5 is connected by way of pipe and passage 20, passage 2i and branch pipe 2 to the brake pipe, it will likewise be depleted of fluid under pressure. The'resulting reduction in thepressure of fluid in chamber I9 to atmospheric pressure willpermit the pressure of the spring 25 acting through the medium of the stop member 22 and follower or stem 27 to actuate the slide valve 26 to its lowermost position, in which position it is shown. Cavity I46 in the slide valve 26 which formerly connected the emergency volume reservoir It to atmosphere as previously noted now establishes communication between pipe MI and said reservoir. Fluid under pressure now flows from chamber I03 in the variable load valve mechanism 8 through passage I06 to pipe IIi'I, whence it flows by way of pipe I08 to service volume reservoir 9 and by way of cavity Mfiin slide valve 26 to pipe MT and emergency volume reservoir l9. When the pressure of fluid in chamber 53 approximates that in chamber iii the various operative parts of the mechanism 3 will'return to the positionin which they are shOWn and th brake cylinder pressure will have been reduced to a degree compatible with safe braking of an empty or partially loaded vehicle.

Referring now to the intercepting valve 'device ll, said device will function as hereinbefore described in connection with a service brake application on an empty vehicle to cut ofi the flow of fluid under pressure from the auxiliary reservoir l3. to the brake controlling valve device 3 when, by reason of the operation of the variable load valve mechanism 8 in this instance, the fluid pressure of the auxiliary reservoir is reduced more than twenty pounds below the pressure at the initiation of the emergency brake application. Thus, if the initial pressure were seventy pounds th auxiliary reservoir pressure will not drop'below approximately fifty pounds, thereby conserving the fluid under pressure in the auxiliary reservoir and aiding in the prevention of excessive brake cylinder pressures. It does not, however, affect the how of fluid under pressure from the emergency reservoir for which the emergency volume reservoir I and the function of the cut-on valve device 4 described in the preceding paragraph are provided.

Release of the brakes after an emergency application and automatic changeover operation of the equipment from empty vehicle to a loaded vehicle condition When it is desired to effect the release of the brakes after an emergency application on a vehicle equipped with the described embodiment of the invention, the brake pipe will be charged with fluid under pressure in the same manner as hereinbefore described in connection with the initial charging of the equipment. As before described, fluid under pressure supplied to the brake pipe I will flow by way of branch pipe 2 to the brake controlling valve device 3, from whence it will flow by way of passage 2| and pipe and passages to cut-oiT valve device 4 and from valve chamber 19 therein to chamber 14 in the locking mechanism 1 by way of connected pipe and passages 15. In response to an increase in the fluid pressure in chamber 14, piston 13 wil1 move downwardly against the pressure of spring 18, thereby causing the locking portion 80 to move out of locking engagement with the toothed portion 84 of the bar 85 and also effecting by way of a check valve device 6 the supply of fluid under pressure to chamber 61 in the measuring apparatus 5. The pressure of fluid thus supplied to chamber 5'! will cause the piston 59 to effect the downward movement of the measuring mechanism 37 until stopped by portion 39 of the mechanism engaging the axle 4U.

Insetting a car out of a train it is the usual practice to effect an emergency application of the brakes.

Assuming now that while the car is thus set out and lading has been placed on the body of the car and under the influence of such additional weight on the vehicle body, the center sill 34 wil1 have moved downwardly relative to the axle 40 by reason of the usual truck springs (not shown) yielding to the additional weight. The space between the center sill 34 and the axle 40, and consequently between the-portion of 7 1'6 themeasuring element-31 and, the axle,-having been shortened because of the yielding of the springunder the influence of the-load, the portion 39'wil1 engage the axle 10 before piston 59 has completed its full stroke. As a result, the-piston 59 will now cause the lever 55 to rotate in a clockwise direction about its lower end which is now in engagement with the roller 54 of the now stationary mechanism 35, the roller of course, being stationary andserving as a fulcrum for the lever. Movement of the upper end of the lever 55 in this direction will be yieldably opposed by the force of the spring 5!! while the piston completes its stroke. The lever 56 as=it-is thus being moved acts to shift the bar 85 and the fulcrum roller 89- associated therewith toward the right along the scale beamlever 94- until such time as the piston comes toa stopat-the end ofits stroke, the distance of travel of the roller 89 being proportional to thedistance of piston travel after the measuring element is brought to a stop by its engagement with the axle. When the brake pipe pressure is increased to the degree required to effect theoperation of cutoff valve device 4, this device will operate, as hereinbefore described, to'vent fluid under pressure from chambers M and 61', and emergency volume reservoir N With'the chamber 14" thus vented, the piston 13 and the stem 19 of the lock"- ing mechanism 1 respond .to the force of the spring 13 to move the locking portion 80 into ongagement with the toothed port-ion 84* ofthe'bar 85' to hold the bar and thereby the fulcrum member 89 in their newly assumed positions.

With the chamber 61 of the load'measuring apparatus 5 vented of fluid under'pres'sure, the spring 62 acts to return the piston 59 andpiston stem 64 to the positionin which they are shown. In so doing, it will cause the lever 66-to be rotated clockwise about the pin 86 whichis now'locke'd, through'the medium of the bar 85 andportion 80, in a position corresponding to the'degree of lading on the vehicle. As the lower end of the lever is withdrawn from engagement with the measuring mechanism 31 the spring 52 will act to retract the mechanism from engagement witl'i'the axle 40 to the position in which it is shown. With the position of the fulcrum member 8'9r'elative to the scale beam lever 94 of the variable load valve mechanism 8 determined according to the amount of movement of piston 59 transferred by the lever 66 from the mechanism tothe fulcrum shifting bar 85, and the transferof movement beingdetermined according to the load on the vehicle, the variable load valve mechanism is now in condition for braking a partially or fully loaded vehicle as the case may be.

Fluid under pressure supplied to the brake pipe I also flows to the chambers at the faces of the service and emergency pistons of the brake'controlling valve device 3, moving the'pistons in due course to release and charging position. Fluid under pressure wil1 then flow into the several chambers of the brake controlling valve device-3, and thence to the emergency reservoir 14 by way of pipe I45 and to chamber 121 in the intercepting valve device I I by way of connected pipe and passage !28. As previously described in connection with the release of the brakes after service application of an equipment conditioned for empty braking, when the pressure of fluid in chamber l2! at the under side of the diaphragm l22 rises to a pressure within less than twenty pounds of that in chamber I23, that is, above fifty pounds,.in this instance, the pressure: or. the

spring I42 will operate to move the guide member I and thereby the valve I31 upwardly until the flange N9 of said valve engages the lowersurface of the wall I30 formed in the casing. With the valve I31 out of engagement with the seat I38, communication is established by which fluid under pressure supplied from the brake pipe I to chambers I2! and I3I flows past valve seat I38, through passage I 25 and pipe I 26 to auxiliary reservoir I3 When the operative parts of the brake controlling valve device 3 move to release position, said device functions to establish communication from the brake cylinder device I2 to atmosphere by way of the retaining valve device I5. Fluid under pressure will flow from the brake cylinder device I2 to the atmospheric passage in the retaining valve device I by way of pipe I49, brake controlling valve device 3 and pipe I50. The brake cylinder device I2 now responds to the release of fluid under pressure therefrom in the usual manner to effect a release of the vehicle brakes.

Fluid under pressure also flows from chambers I2I and H0 in the variable load valve mechanism 8 to atmosphere. being connected to brake cylinder pipe I49 by way of passage H4 and pipe H5. luid under pressure in the service volume reservoir 9 flows by wa of pipe I08, pipeIil'I, assage I90, past back check valve I09 to chamber Ill, and thence by way of passage H3 to chamber H0 and to atmosphere by the same route. It should here be noted that when slide valve 26 of the cut-off valve device 4 was actuated to its uppermost position upon the attain.- ment of thirty pounds pressure in the brake pipe. fluid under pressure in the emergency volume reservoir {0 was connected to atmosphere by way of pipe and passage I41, cavity I45 and passage I48.

Application of the brakes on a partially loaded vehicle When an application of the brakes is made on a partially loaded vehicle by efiecting a reduction in brake pipe pressure. the operation of the brake controlling valve device 3 will be identical with the operation described for an empty ve hicle. From this it will be understood that fluid under pressure will be supplied through pipe I49 to the brake cylinder device I2. from pip I49 by way of pipe H5 and passage IIA to chambers I2! and H0 in the variable load valve mechanism 8 in the manner previously described for the application of the brakes for an empty vehicle.

The pressure of fluid in the chamber I2! deflects the diaphragm 98 and the follower H9 downwardly, thereby rocking lever 94 in a clockwise direction about the fulcrum member 89, which is now located at some point intermediate the position in which it is shown and the right-hand end of the lever 94. When the fluid pressure in said chamber is sufficient to outweigh the opposing pressure of spring I I6 acting upon the left-hand end of lever 94. the resultant clockwise rocking of the lever will cause the diaphragm 91 to deflect upwardly against the stem i0 5 and thereb against the o posing force of the swing I I5 to unseat the valve I04. With the valve unseated, fluid under pressure from the brake cylinder pipe I49 flows through pipe I I5,

passage I I4, valve chamber H0, past the unseated valve I04 and its fluted stem I05, through chamber I03, passage I06, pipe I01 and pipe I08 to the service volume reservoir 9. Whenthe pressure of spring IIS and of fluid in diaphragm chamber I03, and consequently in the reservoir 8, becomes suflicient to counterbalance the pressure of fluid in chamber IZI acting on the lever 94 said lever will be rotated counterclockwise, thereby causing valve I04 to seat and close oil the further flow of fluid under pressure to the volume reservoir 9.

Since the fulcrum member 89 has been adjusted to the right of the position shown, the pressure in chamber I03 will not be as high as -that on an equipment conditioned for empty braking and consequently the brake cylinder pressure will be higher for the additional load. When the vehicle is fully loaded, the fulcrum member will be shifted to its extreme right-hand position, in which position it will prevent entircly the operation of the diaphragm 98 and. of the whole mechanism 8. Fluid in the brake cylinder device I 2 will then build up to its maximum pressure for any particular degree of brake pipe reduction.

As previously stated, the operation of the intercepting valve device II becomes important in controlling the brake when the vehicle is descending a long grade. Preparatory to descending a grade, the retaining valve device I5 is set by turning the handle I-5I from the position in which it is shown in the drawing to a position to retain a predetermined pressure in the brak cylinder device I2 when recharging reservoirs I3 and I l after the initial application. It is to be understood that the pressure retained will be the minimum required to maintain the brake shoes in engagement with the vehicle wheel. In controlling the train on a descending grade it is customary to cycle the brakes, that is, to effect an application of the brakes and recharge the equipment while a partial release of the brakes is taking place through the adjusted retaining valve device, and alternately applying and releasing the brakes. It will be understood that it is highly desirable to have a brake equipment that will provide selectivity of brake operation regardless of the operating pressures and one that will also conserve the braking energy and yet will retain a reasonably heavy brake application available to the train operator.

Attention is therefore directed to the fact that the operator may obtain a brake application equivalent to a twenty pound brake pipe reduction, so long as there is reserve fluid pressure in the equipment, by reason of the device II setting the pressure of fluid in the auxiliary reservoir as a standard (in the closing of valve I32) and measuring a twenty pound reduction therefrom by the weighing of spring I 42 and thereafter isolating the auxiliary reservoir (by the seating of valve I31). By providing a reset for each release operation (in the unseating of valve 132) the operator may again effect a twenty pound reduction in auxiliary reservoir pressure although the auxiliary reservoir has not been recharged to its initial pressure. By preventing an over-reduction in auxiliary reservoir pressure the operator is compelled to conserve his reservoir pressure and at the same time prevent excessive brake cylinder pressure from being attained as a result of an. over-reduction in brake pipe pressure.

Summary Thus, it will be seen from the foregoing that there is provided a variable load brake equipment of the type employing a single brake cylinder and which is automatically adjusted, during the charging of the brake pipe I from atmospheric pressure, to vary the braking force exerted by said brake cylinder for a given reduction n the pressure in the brake pipe according to the weight of the load on the vehicle. As the pressure in the brake pipe is increased above atmospheric pressure during the charging of the brake pipe, the cut-off valve device 4 permits fluid under pressure to flow from the brake pipe I to the locking mechanism 1 which mechanism operates in response to the pressure of fluid thus sup-. plied to unlock the load measuring apparatus I and then to supply fluid under pressure from the brake .pipe to. said apparatus. In response to the pressure of fluid thus supplied, the load measuring apparatus actuates the measuring element 38 intoengagement with the vehicle axle 4t and positions the fulcrum member 89 in the variable load valve mechanism 8 accordingly; When the pressure of fluid in the cut-off valve device reaches a predetermined degree the cut-off valve device operates in response thereto tocut off the further flow of fluid under pressure to the looking mechanism and the load measuring apparatus andconnects said mechanism and apparatus to atmosphere so that first the locking mechaand then the load measuring apparatus are vented.

The apparatus being thus adjusted, when a reduction in the pressure of fluid in the brake pipe is effected, the brakecontrolling valve device 3 will operatesin the usual manner to supply fluid under pressure to the brake cylinder and also to the variable load valve mechanism 8. If the vehicle is" less than fully loaded, the mechanism 8 will operate inresponse to the pressure of fluid thus supplied from the brake controlling valve device to spill or bleed a portion of this fluid under'pressure into the service volume reservoir 9 until the scalev beam lever 94 is balanced, thereby reducing the braking power of the brake cylinder accordingto the weight of the load as determined by the adjustedposition of the fulcrum member 88- in' the variable load valve mechanism 8. If the-vehicle is fully loaded the mechanism 3 will be inoperative because the adjustment for the weight of the load on the vehicle will: be such that the fulcrum. member 89 will be directly under the diaphragm til-sothat deflection of thediaphragm to operate the mechanism will be prevented.

Now, if the reduction of brake pipe pressure should be ofa' degree such that the pressure of fluid in-the' auxiliary reservoir It would be reduced more than pounds below the pressure present in the auxiliary reservoir at the initiation of the brake application, the intercepting valve device I I will limit such reduction in the pressure of fluid in the auxiliary reservoir to 20 pounds by operating in response'to such reduction to out off the" further flow of fluid under pressure from the auxiliary reservoir to the brake controlling valvedevice. If the brakes are alternately applied and released as in cycling on longdescending grades, the intercepting valve device will automatically reset so as to measure aZO-pound reduction from; the degree of pressure present in the auxiliary reservoir at the initiation of that particular brake application.

If the pressure of fluid in the brake pipe is,v reduced to atmosphericpressrure at an emergency rate, the brake controlling valve device will operate in the usual manner to effect an emergency application of the brakes by connecting the emergency reservoir I4 also: to the brake cylinder-de- '20 vice. With the charged volume increased, it becomes necessary to increase the volume into which the fluid under pressure supplied from the brake controlling valve device to the brake cylinder may be spilled. Therefore, when the pressure of fluid in the brake pipe is reduced below application. I

When the brake controlling valve device 3 moves to release position in response to an increase in the pressure of fluid in the brake pipe,

said. device will function to vent fluid under pressure from the brake cylinder device to atmosphere by way of the retaining valve device :5.

From the foregoing it will be readily apparent that since the standard volumes and passages used in the AB freight brake equipment are retained in the use of this invention, the brakeapplication and release times'will be the same as those for the "AB, equipment and therefore this apparatus will operate in harmony with the AB equip-ment, the response to the efiecting of a brake application on the train will be the same regardless of the load on the vehicle, and a brake application equivalent to a 20 pound reduction in the pressure in the brake pipe will always be available to the operator.

Having now described my invention what I claim as new and desire to secure by Letters Patcut, is:

1. In a variable load fluid pressure brake equipment for a vehicle, in combination, a brake cylinder, a brake controlling valve device operative to supply fluid under pressure to the brake cylinder to effect an application of the brakes, a reservoir arranged to receive fluid supplied by the brake controlling valve device to control the pressure of fluid in the brake cylinder, valve means subject to the opposing pressures of fluid in said reservoir and brake cylinder and operative in response to an increase in the pressure of fluid in the reservoir for controlling the amount of fluid flowing to the reservoir, and means operative according to different weights of lading carried by the vehicle for variously conditioning said valve means for response to diflerent reservoir pressures to provide the pressure of fluid in the brake cylinder for any given weight of lading carried by the vehicle.

2. In a variable load fluid pressure brake equip ment for a vehicle, in combination, a brake cylinder, a brake controlling valve device operative to supply fluid under pressure to the brake cylinder to eflect an application of the brakes, a reservoir arranged to receive fluid supplied by the brake controlling valve device to control the pressure of fluid in the brake cylinder, valve means subject to the opposing pressures of fluid in said reservoir and brake cylinder and operative in response to an increase in the pressure of fluid in the reservoir for controlling the amount of fluid flowing to the reservoir, and means operative according to different Weights of lading carried by the vehicle for variously conditioning said valve means for response to different reservoir pressures to provide the pressure of fluid in the brake cylinder for any givenwveight of lading carried by the vehicle, said means being operative 21 when the vehicle is heavily loaded to render said valve means ineffective to permit the flow of fluid from the brake cylinder to said reservoir and thereby render the reservoir ineffective to control the brake cylinder pressure.

3. A vehicle variableload fluid pressure brake equipment, in combination, a brake cylinder device, a volume reservoir, a brake controlling valve device operative to supply fluid under pressure to said brake cylinder device, valve means operative to control the flow of fluid under pressure from said brake controlling valve device to said volume reservoir and to thereby vary the pressure of fluid in said brake cylinder device, and means for adjusting said valve means in accordance with the weight of lading carried by the vehicle for operation in response to variations in the pressure of fluid supplied by said brake controlling valve device to proportion the amount of fluid under pressure which may flow to said volume reservoir inversely to the Weight of the load carried by the vehicle.

4. A vehicle variable load fluid pressure brake equipment in combination, a brake cylinder device, a volume reservoir, a brake controlling valve devic operative to supply fluid under pressure to said brake cylinder device, a valve mechanism interposed between said brake controlling valve device and said volume reservoir for permitting fluid being supplied to the brake cylinder to flow to the volume reservoir and operative in response to an increase in pressure of fluid in said reservoir for cutting ofi the flow of fluid to the reservoir according to the load carried by the vehicle by causing a certain amount of the fluid under pressure being supplied to the brake cylinder device to flow to said volume reservoir, the amount of fluid flowing to the reservoir varying inversely to the load carried by the vehicle, and means for adjusting said valve mechanism in accordance with the weight of the load carried by the vehicle for operation according to variations in the pressure of fluid supplied to the brake cylinder device to control the amount of fluid under pressure flowing to said volume reservoir.

5. In a vehicle variable load fluid pressure brake equipment, in combination, a brake cylinder device, a volume reservoir, a brake controlling valve device operative to supply fluid under pressure to said brake cylinder device, a conduit through which fluid under pressure may flow to said reservoir, and a valve mechanism operative to control the flow of fluid under pressure through said conduit from said brake controlling valve device to said volume reservoir and thereby control the pressure of fluid in said brake cylinder device, said valve mechanism being conditionable when the vehicle is fully loaded to prevent the flow of fluid under pressure to said volume reservoir and for operation according to variations in the pressure of fluid supplied by said brake controlling valve device and being conditionable when the vehicle is empty or partly loaded to provide for metering the fluid under pressure admitted to said volume reservoir in amounts varying inversely proportional to the weights of the load carried by the vehicle, and means operative as an incident to the charging of the equipment with fluid under pressure for conditioning said valve means.

6. In a vehicle variable load fluid pressure brake equipment, in combination, a brake cylinder device for providing braking power on a heavily loaded vehicle, a volume reservoinvalve means arranged to be cut into operation to provide decreased braking power on the vehicle when the vehicle is lightly loaded, means operative according to the load carried by the vehicle for conditioning said valve means for operation in response to any increase in the pressure of fluid in said brake cylinder device to permit proportional amounts of fluid to flow to said volume reservoir, the conditioning of said valve means being diflerout for different loads carried by the vehicle so as to render said valve means operative to provide for the flow of diflerent amounts of fluid under pressure to said volume reservoir and thereby control the braking power of said brake cylinder device according to the load carried by the vehicle,

, 7. The combination with a vehicle fluid pressure brake equipment of the type having a brake cylinder device, a volume reservoir, and a brake controlling valv device for supplying fluid under pressure to said brake cylinder device and said volume reservoir, of adjustable means operative in response to variations in the pressure of fluid supplied by said brake controlling valve device for varying the amount of fluid under pressure flowing from said brake controlling valve device to said volume reservoir to thereby vary the pressure of fluid in said brake cylinder device according to the adjustment of the adjustable means, and means operative in accordance with different weights of lading carried for adjusting said adjustable means, 8. "In a variable load fluid pressure brake. equipment for a vehicle, in combination, a brake cylinder, a brake controlling valve device operative to supply fluid under pressure to the brake cylinder, a volume reservoir, a conduit through which fluid under pressure being supplied by the brake controlling valve device may flow to said reservoir, valve means interposed in said conduit conditioned according to the weight of the lading carried by the vehicle for response to the pressure of the fluid being supplied by the brake controlling valve device for eflecting the flow of fluid through said conduit and for response to the pressure of fluid being supplied to said reservoir for cutting off the flow of fluid through said con duit to provide different pressures of fluid in the brake cylinder for diiferent weights of the lading carried. i

9. In a variable load fluid pressure brake equip ment for a vehicle, in combination, a brake cylinder, a brake controlling valve device operative to supply fluid under pressure to the brake cylinder, a volume reservoir, a conduit through which fluid under pressure being supplied by the brake controlling valve device may flow to said reservoir, valve means interposed in said conduit conditioned according to the weight of the lading carried by the vehicle for response to the pressure of the fluid being supplied by the brake controlling valve device for metering the amount of fluid flowing to said reservoir or for preventing the flow of fluid. thereto to provide diflerent pressures of fluid in the brake cylinder for different weights of lading carried by the vehicle.

10. In a, variable load fluid pressure brake equipment for a vehicle, in combination, a brake cylinder, a brake controlling valve device operative to supply fluid under pressure to the brake cylinder, a volume reservoir, a conduit through which fluid under pressure being supplied by the brake controlling valve device may flow to said reservoir, valve means interposed in said conduit conditioned according to the weight of the lading carried by the vehicle for response to the pres trolling valve devicev for metering the amount of fluid flowing tosaid reservoir to provide different: pressures of fluid in the brake cylinder for different weights of, lading carried by the vehicle.

11'. In a variable load fluid pressure brake equipment for a vehicle, in combination, a brake cylinder, a brake controlling valve device operative to supply fluid under pressure to the brake cylinder to effect an application of the brakes, a fluid reservoir into which fluid under pressure supplied by the brake controlling valve device flows to control the pressure of fluid in the brake cylinder, means subject to the opposing fluid pressures of the reservoir and brake cylinder and operative upon an increase in the pressure of fluid in the reservoir for limiting the amount of fluid flowing to the reservoir, and means adjustable according to different Weights of lading carried by the vehicle for rendering said valve means responsive to different fluid pressures in the reservoir.

12. In a variable load fluid pressure brake equipment for a vehicle, in combination, a brake cylinder,v a brake controlling valve device operative to supply fluid under pressure to the brake cylinder to effect an application of the brakes, a fluid receiver normally at atmospheric pressure for receiving fluid under pressure being supplied to the brake cylinder, a conduit through which the fluid under pressure flows to said fluid receiver.. valve means interposed in said conduit conditioned according to the Weight of the lading carried by the vehicle for response to the pressure of the fluid being supplied by the brake controlling valve device for either effecting the flow of fluid to said receiver and for controlling the amount of fluid flowing thereto or inhibiting the flow of fluid thereto to provide the pressure of fluid inthe brake cylinder called for by the weight of the lading carried by the vehicle.

13; In a vehicle variable load fluid pressure brake equipment of the typev comprising a brake pipe, an auxiliary reservoir, an emergency reservoir, a brake cylinder, and a brake controlling valve device operative in response to a service re duction'; in the pressure of fluid in said brake pipe to connect said auxiliary reservoir to said brake cylinder and operative in response to an emergency reduction in the pressure of fluid in the brake pipe to open communication between both reservoirs and the brake cylinder to effect an application of the brakes, in combination, a service volume reservoir; a variable load valve mecha nism. operative to vary the pressure of fluid in a said brake cylinder by effecting a flow of fluid being supplied to said brake cylinder to said service volume reservoir in amounts varying inversely to the load carried by the vehicle, an emergency volume reservoir, and means operative as a result of an emergency reduction in the pressure of fluid in the brake pipe to establish a communication through which fluid under pressure flows from said service volume reservoir to said emergency volume reservoir.

14. A vehicle variable load fluid pressure brake, in'combination, a brake pipe normally charged with fluid under pressure, an auxiliary reservoir,

an emergency reservoir, a brake cylinder, a brake controlling valve device operative in response to an emergency reduction in the pressure of fluid in said brake pipe to connect the auxiliary and emergency reservoirs to the brake cylinder, a service volume reservoir, an emergency volume reservoir; a variable load valve mechanism, apasoil 24 a sage connecting said mechanism to the volume reservoirs, said variable load valve mechanism being operative to vary the pressure of fluid in said brake cylinder according to variations in the weight of the lading carried by the vehicle by permitting, fluid under pressure being supplied by the brake controlling valve device .to said brake cylinder to flow to said pass-age in amounts varying inversely to the Weight of the lading carried by the vehicle, and valve means interposed in said passage and operative in response to a subsequent increase the pressure of fluid in the brake pipe to effect a release of the brakes .to close communication between said passage and said emergencyvolume reservoir'and to vent fluid under pressure from the emergency volume reservoir.

15. A vehicle variable load fluid pressure brake, in combination, a brake pipe, an auxiliary reservoir, an emergency reservoir, all normally charged with fluid under pressure, a brake cylinder, a brake controlling valve device operative in response to a service reduction in the pressure of fluid in said brake pipe to admit fluid under pressure from said auxiliary reservoir to said brake cylinder and operative in response to an emergency reduction in the pressure of fluid in said brake pipe to admit fluid under pressure from the auxiliary and emergency reservoirs to the brake cylinder, a service volume reservoir, an emergency volume reservoir, a variable load valve mechanism interposed between said brake controlling valve and said servicevolume reservoir and operative to vary the pressure of fluid in said brake cylinder by permitting fluid under pressure supplied from the brake controlling valve device to the brake cylinder toflow to said service volume reservoir in amounts varying inversely to the load carried by the vehicle, said valve mechanism being adjustable in accordance with the Weight of the load carried by the vehicle for operation according to variations in the pressure of fluid supplied to the brake cylinder to permit proportional amounts of fluid under pressure to flow to said service volume reservoir, and valve means subject to the pressure of fluid in the brake pipe and operative in response to an emergency reduction in the pressure of fluid in the brake pipe to connect said emergency volume reservoir to said service volume reservoir.

16. In a vehicle variable load fluid pressure brake equipment of the type comprising a brake pipe, an auxiliary reservoir, an emergency reservoir, a brake cylinder, and a brake controlling valve device operative to effect a service brake application by admitting fluid under pressure from said auxiliary reservoir to said brake cylinder and operative to effect an emergency brake application by admitting fluid under pressure from the auxiliary and the emergency reservoirs to the brake cylinder, in combination, a service volume reservoir, an emergency volume reservoir, a variable load valve mechanism operative to vary the pressure of fluid in said brake cylinder by admitting fluid supplied thereto to the volume reservoirs in amounts varying inversely to the load carried by the vehicle, said mechanism being adjustable in accordance with the weight of the load carried by the vehicle for op eration according to variations in the pressure of fluid suppliedto. said brake cylinder to permit proportional amounts of fluid under pressure to flow to the volume reservoirs, and valve means subject to fluidt under pressure-in theibrake pipe.

and normally closing communication between said variable load valve mechanism and said emergency volume: reservoir, said means being operative as an incident to effecting an emergency application to connect said emergency volume reservoir to said variable load valve mechanism.

17. In a fluid pressure brake equipment, in combination, two fluid pressure supply sources, valve means operative to supply fluid under pres= sure from one of said fluid pressure supply sources to effect aservice application of the brakes and operative to supply fluid under pressure from'said two fluid pressure supply sources .to eifect an emergency application of the brakes, two volume reservoirs normally depleted of fluid under pressure and arranged for receiving fluid under pressure being supplied by the brake controlling valve device, valve means functioning in response to the pressure of fluid being supplied by the brake controlling valve device to establish communication through which fluid under pressure being supplied by the brake controlling valve device may flow to one of said volume reservoirs, and means normally isolating the other of said volume reservoirs from said one volume reservoir and operative as an incident to the effecting of an emergency application of the brakes for opening said other volume reservoir to said one volume reservoir.

18. In a vehicle variable load fluid pressure brake equipment, in combination, two fluid pressure supply sources, valve means operative to supply fluid under pressure from one of said fluid pressure supply sources to effect a service application of the brakes, and operative to sunply fluid under pressure from said two fluid pressure supply sources to effect an emergency application of the brakes, two volume reservoirs normally depleted of fluid under pressure and arranged for receiving fluid under pressure being supplied by said brake controlling valve device, valve means functioning in response to the pressure of fluid being supplied by the brake controlling valve device to establish a communication through which fluid under pressure being supplied by the brake controlling valve device may flow to one of said volume reservoirs, and means normally isolating the other of said volume reservoirs from said one volume reservoir and operative as an incident to the efiecting of an emergency application of the brakes for opening said other volume reservoir to said one volume reservoir, said valve means being conditioned according to various weights of lading carried by the vehicle for operation to correspondingly vary the amount of fluid flowing to one or both of said volume reservoirs for any given amount of fluid under pressure supplied by the brake controlling valve device.

19. In a vehicle variable load fluid pressure brake equipment, a brake pipe normally charged with fluid under pressure, an auxiliary reservoir normally charged with fluid under pressure, an emergency reservoir normally charged with fluid under pressure, a brake cylinder, a brake controlling valve device operative in response to a service reduction in the pressure of fluid in the brake pipe for supplying fluid under pressure from the auxiliary reservoir to said brake cylinder and operative in response to an emergency reduction in the pressure of fluid in the brake pipefor supplying fluid under pressure from both the auxiliary and emergency reservoirs to the brake cylinder; a first volume reservoir normally depleted of fluid under pressure and arranged to 26 receive fluid under pressure being supplied to the brake cylinder by said brake controlling valve device, a second volume reservoir normally depleted of fluid under pressure, means operative in response to said emergency reduction in the pressure of fluid in the brake pipe for establishing a communication through which fluid under pressure being supplied by the brake controlling valve device may flow to said second volum res-.

ervoir, and valve means operative according to various weights of lading carried by the vehicle for variously measuring the amounts of fluid flowing to either said first volume reservoir or to both volume reservoirs.

20. In a vehicle variable load fluid. pressure brake equipment, a brake pipe normally charged with fluid under pressure, an auxiliary reservoir normally charged with fluid under pressure, an emergency reservoir normally charged with fluid under pressure, a brake cylinder, a brake controlling valve device operative in response to a service reduction in the pressure of fluid in the brake pipe for supplying fluid under pressure from the auxiliary reservoir to said brake cylinder and operative in response to an emergency reduction in the pressure of fluid in the brake pipe for supplying fluid under pressure from both the auxiliary and emergency reservoirs to the brake cylinder, a first volume reservoir normally depleted of fluid under pressure and arranged to receive fluid under pressure being supplied to the brake cylinder by said brake controlling valve device, a second Volume reservoir normally depleted of fluid under pressure, means operative in response to said emergency reduction in the pressure of fluid in the brake pipe for establishing a communication through which fluid under pressure being supplied by the brake controlling valve device may flow to said second volume reservoir, and valve means operative according to various weights of lading carried by the vehicle for variously measuring the amounts of fluid flowing to either said first volume reservoir or to both volume reservoirs, said valve means being subject to the opposing pressures of fluidin the brake cylinder and said first volume reservoir and operative upon an increase in the pressure of fluid in the first volume reservoir for controlling the amount of fluid under pressure flowing thereto. i

21. In a vehicle variable load fluid pressure brake equipment, a brake pipe normally charged with fluid under pressure, an auxiliary reservoir normally charged with fluid under pressure, an emergency reservoir normally charged with fluid under pressure, a brake cylinder, a brake controlling valve device operative in response to a service reduction in the pressure of fluid in the brake pipe for supplying fluid under pressure from the auxiliary reservoir to said brake cylinder and operative in response to an emergency reduction in the pressure of fluid in the brake pipe for supplying fluid under pressure from both the auxiliary and emergency reservoirs to the brake cylinder, a first volume reservoir normally depleted of fluid under pressureand arranged to receive fluid under pressure being supplied to the brake cylinder by said brake controlling valve device, a second volume reservoir normally depleted of fluid'under pressure, means operative inresponse to said emergency reduction in the pressure of fluid in the brake pipe for establishing a communication through which fluid under pressure being suppliedby the brake controlling valve device may flow'to said second volume 27 reservoir, and valve means operative according to various weights of the lading carried-bythe vehicle for variously measuring the amounts of fluid flowing to either said first volume reservoir or to both volume reservoirs, said valve means being subject to the opposing pressures of fluid pipe pressure to establish communication through which fluid under pressure is supplied from said auxiliary reservoir to said brake cylinder to effect an application of the brakes, a volume reservoir, a variable load valve mechanism operative to vary the-pressure of fluid supplied to said brake cylinder by permitting fluid under pressure being supplied to the brake cylinder to flow to said volume reservoir in amounts varying inversely to the load carried by the'vehicle, said mechanism being adjustable in accordance with the Weight of the load carried by the vehicle for operation according to variations in the pressure of fluid supplied to said brake cylinder to permit propor tional amounts of fluid under pressure to flow to said volume reservoir, and valve means'responl sive to a predetermined decrease in the pressure of fluid in said auxiliary reservoir for closing said communication to limit the flow of fluid from the auxiliary reservoir to the brake cylinder.

23. In a fluid pressure brake, in combination, a reservoir normally charged with fluid under pressure, -a brake controlling valve device operative to supply fluid under pressure from said reser-voir to effect anapplication of the brakes, and valve means interposed between said reservoir and said brake controlling valve device and operative in response to a chosen reduction in the pressure of fluid in the reservoir and regardless of the rate of such reduction for cutting off the brake cylinder supply of fluid under pressure from the reservoir. 7

24. In a fluid-pressure brake, in combination, a reservoir normally charged with fluid under pressure, a brake controlling valve device operative to supply fluid under pressure from-said resl ervoir to effect an application of the brakes, and valve means interposed between said reservoir and said brake controlling valve device and operative in response to a predetermined reduction in the pressure of fluid in the reservoir for cutting off the brake cylinder supply of fluid under pressure from the reservoir, said valve means being automaticallyconditioned, according to any one of different pressures of fluid to which the reservoir may be charged, for operation'in response to said predetermined reduction in the reservoir pressure below the particular pressure of fluid carried in the reservoir.

25. In a fluid pressure brake equipment, in combination, a brake pipe normally charged with fluid under pressure, an auxiliary reservoir normally chargedwith fluid from the brake pipe and to the same pressure, a-brake cylinder, a service volume reservoir normally at atmospheric pressure and in open communication with said brake cylinder,

a brake controlling valve device operative in response to a full s rvice reduction in brake pipe pressure to supply fluid :under pressure from said auxiliary reservoir to said brake cylinder and service volume reservoir, the pressure of fluid in the auxiliary reservoir being reduced by such supply to a pressure substantially equal to thereduced brake pipe pressure, and valve means operative in response to the reduction in auxiliary reservoir pressure for-inhibiting any further-supply of fluid from the auxiliary reservoir t'o the brake cylinder in the event of afurther reduction'in brake pipe pressure.

'26. In a fluid pressure brake equipment, in combination, a brake pipe normally charged with fluid under pressure, an auxiliary reservoir charged with fluid to a pressure substantially equal to that of the fluid in the brake pipe, a brake cylinder, a brake controlling 'valve'device subject to the opposing pressures of fluid in the brake pipe and auxiliary reservoir and operative in response to a full service reduction in brake pipe-pressure to supply fluid under pressure from said auxiliary reservoir to the brake cylinder, -a service volume reservoir into which fluid under pressure being supplied by the brake controlling valve device to the brake cylinder-also flows, said brake controlling valve device-being operative, when due to the flow of fluid to the brake cylinder and service volume reservoir, the auxiliary reservoir pressure is reduced tosubstantially the reduced brake pipe pressure, to cut-off the flow of fluid to the brake cylinder and service volume reservoir, and meansre'spunsive to the reduction in auxiliary reservoir pressure for inhibiting any further supply of fluid under pressure from the auxiliary reservoir to the brake cylinder in the event of a further reduction in brake pipe pressure.

27. In a fluid pressure brake equipment, in combination, a brake pipe normal-1y charged with fluid under pressure, an auxiliary reservoir charged with fluid to a pressure substantially 'equal'to that of the fluid in the brake pipe, a brake cylinder, a brake controlling valve device subject to the opposing pressures of fluid in the brake pipe, and auxiliary reservoir and operative in response to a full service reductionin brake pipe pressure tosupply fluid .under pressure from said auxiliary reservoir to the brake cylinder, a service volume reservoir into which fluid under pressure being supplied by the brake controlling valve device to the brake cylinder also flowss'aid brake controlling valve device being operative, when due to the flow of fluid to thabrake cylinder. and service volume reservoir, 'the auxiliary reservoir pressure is reduced tosubstantially the reduced brake pipe pressure, to cut-elf the flow of fluid to the brake cylinder-and service volume reservoir, the combined volume of the brake cylinder and service volume reservoir being such with relation to the volume of the :auxiliary reservoir that the brake cylinder pressure attained by said reduction in brake pipe pressure will be lower than the pressure of fluid-remaining in the auxiliary reservoir, and means responsive to the reduction in auxiliary reservoirpressure for inhibiting any further supply of fluid under pressure from the auxiliary reservoir to the brake cylinder in theevent of a further reduction'in brake pipe pressure. 7

28. In a fluid pressure brake equipment in combination, a brake pipe normally charged'with fluid under pressure, an auxiliary reservoir charged with fluid to a pressure substantially 29 equal to that of the fluid in the brake pipe, a brake cylinder, a brake controlling valve device subject to the opposing pressures of fluid in the brake pipe and auxiliary reservoir and operative in response to a full service reduction in brake pipe pressure to supply fluid under pressure from said auxiliary reservoir to the brake cylinder, a service volume reservoir into which fluid under pressure being supplied by the brake controlling valve device to the brake cylinder also flows, said brake controlling valve device being operative, when due to the flow of fluid to the brake cylinder and service volume reservoir, the auxiliary reservoir pressure is reduced to substantially the reduced brake pipe pressure, to cut-off the flow of fluid to the crake cylinder and service volume Cir reservoir, the combined volumes of the brake cylinder and service volume reservoir being such with relation to the volume of the auxiliary reservoir that the brake cylinder pressure attained by said reduction in brake pipe pressure will be lower than the pressure of fluid remaining in the auxiliary reservoir, means responsive to the reduction in auxiliary reservoir pressure for inhibiting any further supply of fluid under pressure from the auxiilary reservoir to the brake cylinder in the event of a further reduction in brake pipe pressure, and valve means operative according to the weight of the lading carried by the vehicle for measuring the amount of fluid under pressure flowing to said service volume reservoir.

EARLE S. COOK.

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